Caesarean babies
at higher asthma risk
Reported June 21, 2008
Babies born by caesarean section are up to 50 per cent
more likely to develop asthma, according to a study of 1.7 million births.
The Norwegian Institute of Public Health research found that the risk of
asthma was even higher in infants who had an emergency caesarean section.
Published in the Journal of Paediatrics, the study looked at babies born in
Norway between 1967 and 1998 and followed the children until 2002 or until
they were 18.
Study author Mette Tollanes said there were two theories to explain why
caesarean born babies were more prone to asthma.
“The first is that babies who are born by caesarean section are not exposed
to their mother’s bacteria during birth, which is detrimental for
development of the immune system,” she said.
“The other is that babies born by caesarean section have more breathing
problems after birth because they are less exposed to stress hormones and
compression of the chest.”
She said stress hormones helped babies empty their lungs of amniotic fluid
and a lack of hormone exposure may affect long-term lung function.
Telethon Institute for Child Health Research paediatric respiratory
physician Peter Sly said the study backed previous findings, including WA
research, which had shown asthma risk was higher in caesarean babies.
“It’s solid data and if there’s a message here, it’s here’s yet another
reason why women should not have elective caesareans,” he said. Thirty per
cent of Australian babies are born by caesarean and WA has the country’s
highest rate at 33 per cent.
Professor Sly said a natural delivery “switched on” many immunological and
hormonal triggers that helped babies prepare for life outside the womb.
“It’s almost like a switching mechanism that says, ‘righto baby you’ve got
to get out into the big wide world, you need this, this and this’, and
without that then a lot of these mechanisms don’t kick in,” he said.
He said caesarean birth alone was unlikely to cause asthma, with genetic
predispositions working in combination with other risk factors.
